CoASH and CoASSG Levels in Lungs of Hyperoxic Rats as Potential Biomarkers of Intramitochondrial Oxidant Stresses

Abstract

Coenzyme A (CoASH) is compartmentalized preferentially in the mitochondria, and CoASH and its mixed disulfide with glutathione (CoASSG) undergo thiol/disulfide exchange reactions with glutathione (GSH) and glutathione disulfide (GSSG) in vitro. We measured CoASH and CoASSG in freeze-clamped lung tissues from Fischer-344 and Sprague-Dawley rats maintained in room air or exposed to Ͼ95% O 2 for 48 h to test the hypothesis that oxidant stresses on lung thiol status would be observed in the CoASH/CoASSG redox couple, suggesting oxidant stress responses in the mitochondria. Lung tissue concentrations of CoASSG in the Fischer-344 rats declined from 0.89 Ϯ 0.15 to 0.51 Ϯ 0.13 nmol/g of lung after 48 h of hyperoxia. CoASH levels declined from 6.40 Ϯ 0.84 to 3.0 Ϯ 0.65 nmol/g of lung, and acetyl CoA levels also were lower in the lungs of animals exposed to hyperoxia. CoASH/CoASSG ratios were lower in animals exposed to hyperoxia, satisfying our previously defined criteria for an oxidant stress on this thiol/disulfide redox couple, but absolute CoASSG levels were not increased, as would be expected for oxidant stresses driven simply by increases in reactive oxygen species or other oxidants. Pulmonary edema was observed in the hyperoxic rats and accounted for some of the declines in CoASH concentrations, but CoASH contents per total lung also declined. Lung mitochondrial succinate dehydrogenase activities were not diminished in rats exposed to hyperoxia, indicating that the decreases in CoASH concentrations are not attributable to general destruction of lung mitochondria. Lung GSSG contents were greater in the hyperoxia animals, but GSH/GSSG ratios, which are dominated by extramitochondrial pools, did not decrease in these animals. The mechanisms responsible for, and the possible pathophysiologic consequences of, the decreases in lung CoASH concentrations are not evident from the data available at the present time, but the loss of more than half the tissue contents of CoASH is likely to generate additional metabolic effects that could have significant pathophysiologic consequences. Administration of supplemental oxygen remains an important therapy in the care of patients with pulmonary insufficiency, as is encountered in many prematurely born infants or in adults with acute respiratory distress. However, this supplemental oxygen can cause adverse effects, as has been observed in the lungs of experimental animals and humans exposed to elevated oxygen tensions (1-4). Cellular injury is manifested when the rates of generation of the reactive species are increased beyond the capacities of the antioxidant defense mechanisms, such as with exposure to hyperoxia (1,5,6), or when the functions of the antioxidant defense mechanisms are deficient, compromised, or developmentally unprepared, such as in prematurely born infants (3,7,8).In the course of exposure of experimental animals to Ͼ95% oxygen, a relatively prolonged period usually is observed in

Effects of Fasting on Tissue Contents of Coenzyme A and Related Intermediates in Rats

“…The losses in CoASH are not offset by increases in CoASSG, as might have been expected with a simple redox shift, but the data presently available do suggest that the decreases in lung CoASH levels represent some form of secondary oxidant stress response. Fasting for 48 h caused declines in lung GSH concentrations and contents and in GSSG contents, in contrast with what we have observed in exposure of these animals to hyperoxia (28).…”

“…The decreases in lung CoASH contents we observed in previous studies of rats exposed to Ͼ95% O 2 (28) do not seem to be mediated by diminished food intake caused by exposure of the animals to hyperoxia. Thus, the effects of hyperoxia on lung CoASH contents are more attributable to other effects of hyperoxia.…”

“…Although decreases in lung contents of GSH in animals exposed to hyperoxia have not been observed in most studies reported to date (21,22,28,38,39), fasting or limiting dietary protein intake can potentiate or accelerate the emergence of lung damage in animals exposed to hyperoxia (21, 39 -41). The increase in animal sensitivity to normobaric hyperoxia was paralleled by attenuation or prevention of the increases in lung GSH levels usually observed in animals fed normal diets after 24 to 48 h of normobaric hyperoxia.…”

The Effect of Inhaled Nitric Oxide and Oxygen on the Hydroxylation of Salicylate in Rat Lungs

“…The rats exposed to 90% O 2 had the highest 2,3-DHBA and the highest lung wet weight. This finding is consistent with previous studies that have demonstrated that a hallmark of hyperoxic lung injury is pulmonary edema (13,35,36). It is of interest to note that the rats exposed to 90% O 2 ϩ 100 ppm NO had the greatest lung wet weight but did not have the greatest 2,3-DHBA.…”

Mitochondrial involvement and oxidative stress in temporal lobe epilepsy

“…Coenzyme A (CoASH) and its disulfide with GSH (CoASSG), primary compartmentalized within mitochondria, have been measured and utilized as a marker of mitochondrial specific redox status [61,62]. GSSG levels have been found to increase as early as 4 hours post-SE in the cortex [24].…”